1. Field of the Invention
The present invention relates to a semiconductor device having a titanium nitride film and a manufacturing method thereof.
2. Description of the Background Art
Conventionally, in a capacitor in which a high dielectrics of a metal oxide such as Ta2O5, HfO2, BaSrTiO3 or the like is used as a dielectric layer, a titanium nitride film (hereinafter referred to as a TiN film) formed by the chemical vapor deposition method (hereinafter referred to as the CVD method) has been used as an upper electrode. Generally, the manufacturing condition of this TiN film involves use of titanium halide gas (for example, TiCl4 gas) and ammonium gas (NH3 gas) as material gases at a deposition temperature of about 600° C.
However, in a case of an MIS (Metal Insulator Silicon) capacitor in which polysilicon is used for the lower electrode and an MIM (Metal Insulator Metal) capacitor in which metal or a metal conductive nitride is used for the lower electrode, there has been a problem that leakage current in the capacitor increases if a TiN film of the upper electrode is formed at 600° C. Accordingly, the TiN film has been formed at the deposition temperature that is lowered to 400° C.-500° C. (for example, see Japanese Patent Laying-Open No. 08-279558).
On the other hand, while the leakage current of a capacitor decreases when the deposition temperature of the TiN film is lowered to at most 500° C., an irregularly grown object is generated. Such an irregularly grown object remains as an etching residue when the TiN film that is the upper electrode is processed, whereby the upper electrode and a contact plug that otherwise should be insulated are brought into electrical contact. This may result in malfunction of the semiconductor device.
Furthermore, as for a transistor expected to be the transistor of the next generation in which a high dielectrics such as HfO2 is used as a gate insulator layer, there is a need for lowering the temperature at which a TiN film to be a gate electrode is formed. Here, crystallization occurs by the thermal hysteresis of 450° C.-500° C. with the aforementioned metal oxide of high permittivity, and an electric conduction through grain boundary of crystals or defect level resulted thereby may undesirably increase the leakage current. On the other hand, when the deposition temperature of the TiN film is lowered to at most 400° C., a large number of irregularly grown objects are generated in the TiN film. Accordingly, if tungsten (hereinafter referred to as W) or the like is further embedded as a gate electrode, the cross section of W is reduced at the portion where the irregularly grown objects are present in the TiN film and current focuses to W having smaller electric resistance as compared to TiN, whereby the electromigration life is significantly reduced.